Bimetallic article



Patented Mar. 12, 1935 UNITED STATES BIMETAILIC ARTICLE Herbert W. Graham and SamueLL. Case, Pitt s-- burgh, Pa., assiguors to Jones & Laughlin Steel Corporation. Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application March 16,1933,

- Serial No. 661,092

2 Claims. (01'. 29-181) This invention relates to bimetallic bodies and particularly to ferrous bodies having a protec-. tive coating of tin.

Commercial tin plate is used in increasingly large amounts for containers to hold food and other commodities. As is well known, it consists of a sheet of steel which has been fed through a tin pot so as to 'coat bothv surfaces with tin. The tin represents only a vary small percentage of the total weight of the sheet, but if properly applied it affords substantial protection to the base metal. Tin plate as. ordinarily. made is open to definite limitations. For example, certain food products such as black cherries cannot be successfully put up in tin cans because after a very short storage the contents of the can are discolored and the taste is spoiled, by reason of 3 the iron in the base metal being attacked and going into solution. A great deal of difiiculty is also experienced in canning corn. These limitations have necessitated the use ofglass containers for certain products and it has also been proposed in the case of army rations, which may be shelved, for a period of years before us-' ing, that stainless steel containers be employed.

This, of course, is'highly expensive.

Study of the problem shows that if, as is frequently the case, a 'very slight pr n hole is present in the tin, or if the coating is thin at some point and deteriorates sufficiently to, allow access of moisture to the ferrous base, local electrolysis to the tin. while as stated, the tin in ordinary tin plate causes the iron to be attacked, we have made the surprising discovery that if sodium even in amounts as low as 0.2% is alloyed with the tin the alloy acts to inhibit the attack on the iron. Up to 2% sodium may be used. If iron and tin are placed 'in any liquid which acts as an electrolyte, the iron will be" attacked. If, however, a small percentage of sodium is added to the tin, the tin-sodium'alloy saves the iron danger of spoilage is materially reduced. We also'believe that the presence of the sodium in the tin improves the tinning operation, resulting in a smaller percentage of waste sheets, a decreased number of pin holes, etc.

We havedescribed a present preferred embodiment of our invention. It will be understood,

however, that this is by way of illustration only and that it may be otherwise embodied or practiced within the scope of the following claims.

We claim:

1. As a new manufacture, a food container made of a bimetallic body comprising a ferrous base and coated with a binary tin-sodium alloy, the sodium being in amount up to 2%.

2. A bimetallic body comprising a ferrous base having directly applied thereto a binary alloy of tin and sodium, the sodium being present in the alloy in an amount up to 2%.

HERBERT W. GRAHAM. SAMUEL L. CASE. 

